
/* Copyright 1998 by the Massachusetts Institute of Technology.
 *
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright
 * notice and this permission notice appear in supporting
 * documentation, and that the name of M.I.T. not be used in
 * advertising or publicity pertaining to distribution of the
 * software without specific, written prior permission.
 * M.I.T. makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is"
 * without express or implied warranty.
 */

#include "ares_setup.h"

#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#ifdef HAVE_NETDB_H
#include <netdb.h>
#endif
#ifdef HAVE_ARPA_NAMESER_H
#include <arpa/nameser.h>
#else
#include "nameser.h"
#endif
#ifdef HAVE_ARPA_NAMESER_COMPAT_H
#include <arpa/nameser_compat.h>
#endif

#ifdef HAVE_STRINGS_H
#include <strings.h>
#endif

#include "ares.h"
#include "ares_dns.h"
#include "ares_nowarn.h"
#include "ares_private.h"

int ares_parse_ptr_reply(const unsigned char* abuf, int alen, const void* addr,
    int addrlen, int family, struct hostent** host)
{
    unsigned int qdcount, ancount;
    int status, i, rr_type, rr_class, rr_len;
    long len;
    const unsigned char* aptr;
    char *ptrname, *hostname, *rr_name, *rr_data;
    struct hostent* hostent;
    int aliascnt = 0;
    int alias_alloc = 8;
    char** aliases;

    /* Set *host to NULL for all failure cases. */
    *host = NULL;

    /* Give up if abuf doesn't have room for a header. */
    if (alen < HFIXEDSZ)
        return ARES_EBADRESP;

    /* Fetch the question and answer count from the header. */
    qdcount = DNS_HEADER_QDCOUNT(abuf);
    ancount = DNS_HEADER_ANCOUNT(abuf);
    if (qdcount != 1)
        return ARES_EBADRESP;

    /* Expand the name from the question, and skip past the question. */
    aptr = abuf + HFIXEDSZ;
    status = ares__expand_name_for_response(aptr, abuf, alen, &ptrname, &len);
    if (status != ARES_SUCCESS)
        return status;
    if (aptr + len + QFIXEDSZ > abuf + alen) {
        ares_free(ptrname);
        return ARES_EBADRESP;
    }
    aptr += len + QFIXEDSZ;

    /* Examine each answer resource record (RR) in turn. */
    hostname = NULL;
    aliases = ares_malloc(alias_alloc * sizeof(char*));
    if (!aliases) {
        ares_free(ptrname);
        return ARES_ENOMEM;
    }
    for (i = 0; i < (int)ancount; i++) {
        /* Decode the RR up to the data field. */
        status = ares__expand_name_for_response(aptr, abuf, alen, &rr_name, &len);
        if (status != ARES_SUCCESS)
            break;
        aptr += len;
        if (aptr + RRFIXEDSZ > abuf + alen) {
            ares_free(rr_name);
            status = ARES_EBADRESP;
            break;
        }
        rr_type = DNS_RR_TYPE(aptr);
        rr_class = DNS_RR_CLASS(aptr);
        rr_len = DNS_RR_LEN(aptr);
        aptr += RRFIXEDSZ;
        if (aptr + rr_len > abuf + alen) {
            ares_free(rr_name);
            status = ARES_EBADRESP;
            break;
        }

        if (rr_class == C_IN && rr_type == T_PTR
            && strcasecmp(rr_name, ptrname) == 0) {
            /* Decode the RR data and set hostname to it. */
            status = ares__expand_name_for_response(aptr, abuf, alen, &rr_data,
                &len);
            if (status != ARES_SUCCESS) {
                ares_free(rr_name);
                break;
            }
            if (hostname)
                ares_free(hostname);
            hostname = rr_data;
            aliases[aliascnt] = ares_malloc((strlen(rr_data) + 1) * sizeof(char));
            if (!aliases[aliascnt]) {
                ares_free(rr_name);
                status = ARES_ENOMEM;
                break;
            }
            strncpy(aliases[aliascnt], rr_data, strlen(rr_data) + 1);
            aliascnt++;
            if (aliascnt >= alias_alloc) {
                char** ptr;
                alias_alloc *= 2;
                ptr = ares_realloc(aliases, alias_alloc * sizeof(char*));
                if (!ptr) {
                    ares_free(rr_name);
                    status = ARES_ENOMEM;
                    break;
                }
                aliases = ptr;
            }
        }

        if (rr_class == C_IN && rr_type == T_CNAME) {
            /* Decode the RR data and replace ptrname with it. */
            status = ares__expand_name_for_response(aptr, abuf, alen, &rr_data,
                &len);
            if (status != ARES_SUCCESS) {
                ares_free(rr_name);
                break;
            }
            ares_free(ptrname);
            ptrname = rr_data;
        }

        ares_free(rr_name);
        aptr += rr_len;
        if (aptr > abuf + alen) { /* LCOV_EXCL_START: already checked above */
            status = ARES_EBADRESP;
            break;
        } /* LCOV_EXCL_STOP */
    }

    if (status == ARES_SUCCESS && !hostname)
        status = ARES_ENODATA;
    if (status == ARES_SUCCESS) {
        /* We got our answer.  Allocate memory to build the host entry. */
        hostent = ares_malloc(sizeof(struct hostent));
        if (hostent) {
            hostent->h_addr_list = ares_malloc(2 * sizeof(char*));
            if (hostent->h_addr_list) {
                hostent->h_addr_list[0] = ares_malloc(addrlen);
                if (hostent->h_addr_list[0]) {
                    hostent->h_aliases = ares_malloc((aliascnt + 1) * sizeof(char*));
                    if (hostent->h_aliases) {
                        /* Fill in the hostent and return successfully. */
                        hostent->h_name = hostname;
                        for (i = 0; i < aliascnt; i++)
                            hostent->h_aliases[i] = aliases[i];
                        hostent->h_aliases[aliascnt] = NULL;
                        hostent->h_addrtype = aresx_sitoss(family);
                        hostent->h_length = aresx_sitoss(addrlen);
                        memcpy(hostent->h_addr_list[0], addr, addrlen);
                        hostent->h_addr_list[1] = NULL;
                        *host = hostent;
                        ares_free(aliases);
                        ares_free(ptrname);
                        return ARES_SUCCESS;
                    }
                    ares_free(hostent->h_addr_list[0]);
                }
                ares_free(hostent->h_addr_list);
            }
            ares_free(hostent);
        }
        status = ARES_ENOMEM;
    }
    for (i = 0; i < aliascnt; i++)
        if (aliases[i])
            ares_free(aliases[i]);
    ares_free(aliases);
    if (hostname)
        ares_free(hostname);
    ares_free(ptrname);
    return status;
}
